CentrED/Imaging/JpegLib/imjdinput.pas

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unit imjdinput;
{ Original: jdinput.c ; Copyright (C) 1991-1997, Thomas G. Lane. }
{ This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.
This file contains input control logic for the JPEG decompressor.
These routines are concerned with controlling the decompressor's input
processing (marker reading and coefficient decoding). The actual input
reading is done in jdmarker.c, jdhuff.c, and jdphuff.c. }
interface
{$I imjconfig.inc}
uses
imjmorecfg,
imjpeglib,
imjdeferr,
imjerror,
imjinclude, imjutils;
{ Initialize the input controller module.
This is called only once, when the decompression object is created. }
{GLOBAL}
procedure jinit_input_controller (cinfo : j_decompress_ptr);
implementation
{ Private state }
type
my_inputctl_ptr = ^my_input_controller;
my_input_controller = record
pub : jpeg_input_controller; { public fields }
inheaders : boolean; { TRUE until first SOS is reached }
end; {my_input_controller;}
{ Forward declarations }
{METHODDEF}
function consume_markers (cinfo : j_decompress_ptr) : int; forward;
{ Routines to calculate various quantities related to the size of the image. }
{LOCAL}
procedure initial_setup (cinfo : j_decompress_ptr);
{ Called once, when first SOS marker is reached }
var
ci : int;
compptr : jpeg_component_info_ptr;
begin
{ Make sure image isn't bigger than I can handle }
if (long(cinfo^.image_height) > long (JPEG_MAX_DIMENSION)) or
(long(cinfo^.image_width) > long(JPEG_MAX_DIMENSION)) then
ERREXIT1(j_common_ptr(cinfo), JERR_IMAGE_TOO_BIG, uInt(JPEG_MAX_DIMENSION));
{ For now, precision must match compiled-in value... }
if (cinfo^.data_precision <> BITS_IN_JSAMPLE) then
ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PRECISION, cinfo^.data_precision);
{ Check that number of components won't exceed internal array sizes }
if (cinfo^.num_components > MAX_COMPONENTS) then
ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, cinfo^.num_components,
MAX_COMPONENTS);
{ Compute maximum sampling factors; check factor validity }
cinfo^.max_h_samp_factor := 1;
cinfo^.max_v_samp_factor := 1;
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
if (compptr^.h_samp_factor<=0) or (compptr^.h_samp_factor>MAX_SAMP_FACTOR) or
(compptr^.v_samp_factor<=0) or (compptr^.v_samp_factor>MAX_SAMP_FACTOR) then
ERREXIT(j_common_ptr(cinfo), JERR_BAD_SAMPLING);
{cinfo^.max_h_samp_factor := MAX(cinfo^.max_h_samp_factor,
compptr^.h_samp_factor);
cinfo^.max_v_samp_factor := MAX(cinfo^.max_v_samp_factor,
compptr^.v_samp_factor);}
if cinfo^.max_h_samp_factor < compptr^.h_samp_factor then
cinfo^.max_h_samp_factor := compptr^.h_samp_factor;
if cinfo^.max_v_samp_factor < compptr^.v_samp_factor then
cinfo^.max_v_samp_factor := compptr^.v_samp_factor;
Inc(compptr);
end;
{ We initialize DCT_scaled_size and min_DCT_scaled_size to DCTSIZE.
In the full decompressor, this will be overridden by jdmaster.c;
but in the transcoder, jdmaster.c is not used, so we must do it here. }
cinfo^.min_DCT_scaled_size := DCTSIZE;
{ Compute dimensions of components }
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
compptr^.DCT_scaled_size := DCTSIZE;
{ Size in DCT blocks }
compptr^.width_in_blocks := JDIMENSION(
jdiv_round_up( long(cinfo^.image_width) * long(compptr^.h_samp_factor),
long(cinfo^.max_h_samp_factor * DCTSIZE)) );
compptr^.height_in_blocks := JDIMENSION (
jdiv_round_up(long (cinfo^.image_height) * long(compptr^.v_samp_factor),
long (cinfo^.max_v_samp_factor * DCTSIZE)) );
{ downsampled_width and downsampled_height will also be overridden by
jdmaster.c if we are doing full decompression. The transcoder library
doesn't use these values, but the calling application might. }
{ Size in samples }
compptr^.downsampled_width := JDIMENSION (
jdiv_round_up(long (cinfo^.image_width) * long(compptr^.h_samp_factor),
long (cinfo^.max_h_samp_factor)) );
compptr^.downsampled_height := JDIMENSION (
jdiv_round_up(long (cinfo^.image_height) * long(compptr^.v_samp_factor),
long (cinfo^.max_v_samp_factor)) );
{ Mark component needed, until color conversion says otherwise }
compptr^.component_needed := TRUE;
{ Mark no quantization table yet saved for component }
compptr^.quant_table := NIL;
Inc(compptr);
end;
{ Compute number of fully interleaved MCU rows. }
cinfo^.total_iMCU_rows := JDIMENSION(
jdiv_round_up(long(cinfo^.image_height),
long(cinfo^.max_v_samp_factor*DCTSIZE)) );
{ Decide whether file contains multiple scans }
if (cinfo^.comps_in_scan < cinfo^.num_components) or
(cinfo^.progressive_mode) then
cinfo^.inputctl^.has_multiple_scans := TRUE
else
cinfo^.inputctl^.has_multiple_scans := FALSE;
end;
{LOCAL}
procedure per_scan_setup (cinfo : j_decompress_ptr);
{ Do computations that are needed before processing a JPEG scan }
{ cinfo^.comps_in_scan and cinfo^.cur_comp_info[] were set from SOS marker }
var
ci, mcublks, tmp : int;
compptr : jpeg_component_info_ptr;
begin
if (cinfo^.comps_in_scan = 1) then
begin
{ Noninterleaved (single-component) scan }
compptr := cinfo^.cur_comp_info[0];
{ Overall image size in MCUs }
cinfo^.MCUs_per_row := compptr^.width_in_blocks;
cinfo^.MCU_rows_in_scan := compptr^.height_in_blocks;
{ For noninterleaved scan, always one block per MCU }
compptr^.MCU_width := 1;
compptr^.MCU_height := 1;
compptr^.MCU_blocks := 1;
compptr^.MCU_sample_width := compptr^.DCT_scaled_size;
compptr^.last_col_width := 1;
{ For noninterleaved scans, it is convenient to define last_row_height
as the number of block rows present in the last iMCU row. }
tmp := int (LongInt(compptr^.height_in_blocks) mod compptr^.v_samp_factor);
if (tmp = 0) then
tmp := compptr^.v_samp_factor;
compptr^.last_row_height := tmp;
{ Prepare array describing MCU composition }
cinfo^.blocks_in_MCU := 1;
cinfo^.MCU_membership[0] := 0;
end
else
begin
{ Interleaved (multi-component) scan }
if (cinfo^.comps_in_scan <= 0) or (cinfo^.comps_in_scan > MAX_COMPS_IN_SCAN) then
ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, cinfo^.comps_in_scan,
MAX_COMPS_IN_SCAN);
{ Overall image size in MCUs }
cinfo^.MCUs_per_row := JDIMENSION (
jdiv_round_up(long (cinfo^.image_width),
long (cinfo^.max_h_samp_factor*DCTSIZE)) );
cinfo^.MCU_rows_in_scan := JDIMENSION (
jdiv_round_up(long (cinfo^.image_height),
long (cinfo^.max_v_samp_factor*DCTSIZE)) );
cinfo^.blocks_in_MCU := 0;
for ci := 0 to pred(cinfo^.comps_in_scan) do
begin
compptr := cinfo^.cur_comp_info[ci];
{ Sampling factors give # of blocks of component in each MCU }
compptr^.MCU_width := compptr^.h_samp_factor;
compptr^.MCU_height := compptr^.v_samp_factor;
compptr^.MCU_blocks := compptr^.MCU_width * compptr^.MCU_height;
compptr^.MCU_sample_width := compptr^.MCU_width * compptr^.DCT_scaled_size;
{ Figure number of non-dummy blocks in last MCU column & row }
tmp := int (LongInt(compptr^.width_in_blocks) mod compptr^.MCU_width);
if (tmp = 0) then
tmp := compptr^.MCU_width;
compptr^.last_col_width := tmp;
tmp := int (LongInt(compptr^.height_in_blocks) mod compptr^.MCU_height);
if (tmp = 0) then
tmp := compptr^.MCU_height;
compptr^.last_row_height := tmp;
{ Prepare array describing MCU composition }
mcublks := compptr^.MCU_blocks;
if (LongInt(cinfo^.blocks_in_MCU) + mcublks > D_MAX_BLOCKS_IN_MCU) then
ERREXIT(j_common_ptr(cinfo), JERR_BAD_MCU_SIZE);
while (mcublks > 0) do
begin
Dec(mcublks);
cinfo^.MCU_membership[cinfo^.blocks_in_MCU] := ci;
Inc(cinfo^.blocks_in_MCU);
end;
end;
end;
end;
{ Save away a copy of the Q-table referenced by each component present
in the current scan, unless already saved during a prior scan.
In a multiple-scan JPEG file, the encoder could assign different components
the same Q-table slot number, but change table definitions between scans
so that each component uses a different Q-table. (The IJG encoder is not
currently capable of doing this, but other encoders might.) Since we want
to be able to dequantize all the components at the end of the file, this
means that we have to save away the table actually used for each component.
We do this by copying the table at the start of the first scan containing
the component.
The JPEG spec prohibits the encoder from changing the contents of a Q-table
slot between scans of a component using that slot. If the encoder does so
anyway, this decoder will simply use the Q-table values that were current
at the start of the first scan for the component.
The decompressor output side looks only at the saved quant tables,
not at the current Q-table slots. }
{LOCAL}
procedure latch_quant_tables (cinfo : j_decompress_ptr);
var
ci, qtblno : int;
compptr : jpeg_component_info_ptr;
qtbl : JQUANT_TBL_PTR;
begin
for ci := 0 to pred(cinfo^.comps_in_scan) do
begin
compptr := cinfo^.cur_comp_info[ci];
{ No work if we already saved Q-table for this component }
if (compptr^.quant_table <> NIL) then
continue;
{ Make sure specified quantization table is present }
qtblno := compptr^.quant_tbl_no;
if (qtblno < 0) or (qtblno >= NUM_QUANT_TBLS) or
(cinfo^.quant_tbl_ptrs[qtblno] = NIL) then
ERREXIT1(j_common_ptr(cinfo), JERR_NO_QUANT_TABLE, qtblno);
{ OK, save away the quantization table }
qtbl := JQUANT_TBL_PTR(
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
SIZEOF(JQUANT_TBL)) );
MEMCOPY(qtbl, cinfo^.quant_tbl_ptrs[qtblno], SIZEOF(JQUANT_TBL));
compptr^.quant_table := qtbl;
end;
end;
{ Initialize the input modules to read a scan of compressed data.
The first call to this is done by jdmaster.c after initializing
the entire decompressor (during jpeg_start_decompress).
Subsequent calls come from consume_markers, below. }
{METHODDEF}
procedure start_input_pass (cinfo : j_decompress_ptr);
begin
per_scan_setup(cinfo);
latch_quant_tables(cinfo);
cinfo^.entropy^.start_pass (cinfo);
cinfo^.coef^.start_input_pass (cinfo);
cinfo^.inputctl^.consume_input := cinfo^.coef^.consume_data;
end;
{ Finish up after inputting a compressed-data scan.
This is called by the coefficient controller after it's read all
the expected data of the scan. }
{METHODDEF}
procedure finish_input_pass (cinfo : j_decompress_ptr);
begin
cinfo^.inputctl^.consume_input := consume_markers;
end;
{ Read JPEG markers before, between, or after compressed-data scans.
Change state as necessary when a new scan is reached.
Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
The consume_input method pointer points either here or to the
coefficient controller's consume_data routine, depending on whether
we are reading a compressed data segment or inter-segment markers. }
{METHODDEF}
function consume_markers (cinfo : j_decompress_ptr) : int;
var
val : int;
inputctl : my_inputctl_ptr;
begin
inputctl := my_inputctl_ptr (cinfo^.inputctl);
if (inputctl^.pub.eoi_reached) then { After hitting EOI, read no further }
begin
consume_markers := JPEG_REACHED_EOI;
exit;
end;
val := cinfo^.marker^.read_markers (cinfo);
case (val) of
JPEG_REACHED_SOS: { Found SOS }
begin
if (inputctl^.inheaders) then
begin { 1st SOS }
initial_setup(cinfo);
inputctl^.inheaders := FALSE;
{ Note: start_input_pass must be called by jdmaster.c
before any more input can be consumed. jdapimin.c is
responsible for enforcing this sequencing. }
end
else
begin { 2nd or later SOS marker }
if (not inputctl^.pub.has_multiple_scans) then
ERREXIT(j_common_ptr(cinfo), JERR_EOI_EXPECTED); { Oops, I wasn't expecting this! }
start_input_pass(cinfo);
end;
end;
JPEG_REACHED_EOI: { Found EOI }
begin
inputctl^.pub.eoi_reached := TRUE;
if (inputctl^.inheaders) then
begin { Tables-only datastream, apparently }
if (cinfo^.marker^.saw_SOF) then
ERREXIT(j_common_ptr(cinfo), JERR_SOF_NO_SOS);
end
else
begin
{ Prevent infinite loop in coef ctlr's decompress_data routine
if user set output_scan_number larger than number of scans. }
if (cinfo^.output_scan_number > cinfo^.input_scan_number) then
cinfo^.output_scan_number := cinfo^.input_scan_number;
end;
end;
JPEG_SUSPENDED:;
end;
consume_markers := val;
end;
{ Reset state to begin a fresh datastream. }
{METHODDEF}
procedure reset_input_controller (cinfo : j_decompress_ptr);
var
inputctl : my_inputctl_ptr;
begin
inputctl := my_inputctl_ptr (cinfo^.inputctl);
inputctl^.pub.consume_input := consume_markers;
inputctl^.pub.has_multiple_scans := FALSE; { "unknown" would be better }
inputctl^.pub.eoi_reached := FALSE;
inputctl^.inheaders := TRUE;
{ Reset other modules }
cinfo^.err^.reset_error_mgr (j_common_ptr(cinfo));
cinfo^.marker^.reset_marker_reader (cinfo);
{ Reset progression state -- would be cleaner if entropy decoder did this }
cinfo^.coef_bits := NIL;
end;
{ Initialize the input controller module.
This is called only once, when the decompression object is created. }
{GLOBAL}
procedure jinit_input_controller (cinfo : j_decompress_ptr);
var
inputctl : my_inputctl_ptr;
begin
{ Create subobject in permanent pool }
inputctl := my_inputctl_ptr(
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_PERMANENT,
SIZEOF(my_input_controller)) );
cinfo^.inputctl := jpeg_input_controller_ptr(inputctl);
{ Initialize method pointers }
inputctl^.pub.consume_input := consume_markers;
inputctl^.pub.reset_input_controller := reset_input_controller;
inputctl^.pub.start_input_pass := start_input_pass;
inputctl^.pub.finish_input_pass := finish_input_pass;
{ Initialize state: can't use reset_input_controller since we don't
want to try to reset other modules yet. }
inputctl^.pub.has_multiple_scans := FALSE; { "unknown" would be better }
inputctl^.pub.eoi_reached := FALSE;
inputctl^.inheaders := TRUE;
end;
end.